This invention relates to Foley Catheters, and particularly Foley Catheters having temperature sensors.
The disclosures of U.S. Pat. No. 6,019,783, issued Feb. 1, 2000, U.S. Pat. No. 6,126,684, issued Oct. 3, 2000, and U.S. Pat. No. 6,146,411, issued Nov. 14, 2000, are incorporated herein by reference.
Foley catheters typically include a soft, thin rubber tube with a balloon on one end. The catheter is threaded through the urinary duct (urethra) and into the bladder to drain urine from the bladder. A Foley catheter is typically used when normal urination is disrupted by an infection, a swollen prostate gland, bladder stones, or, sometimes, an injury. In very sick people, a catheter may be used to keep track of urine production.
A typical Foley catheter has drainage lumen, and an inflation lumen for inflating and deflating the balloon. The balloon is normally deflated until properly positioned in a patient""s bladder. Once the catheter is properly positioned, the inflation lumen delivers fluid to inflate the balloon. The inflated balloon holds the catheter in place.
There are risks associated with the use of a Foley catheter. For example, the bladder or urethra could be injured when the Foley catheter is inserted. Infection is also possible. Patients may find the process of insertion of a Foley catheter unpleasant and sometimes painful.
The bladder is an accepted situs for core body temperature measurements. Accordingly, some Foley catheters include a temperature sensor included on the end of the catheter. A wire connects the sensor, via the catheter, to externally located monitoring devices.
One drawback to Foley catheters with a temperature sensor is that the sensor may fail. When the sensor fails, the failed catheter may have to be replaced. This not only compounds patient discomfort, but also increases the risk of injury and infection for the patient. A further risk is that the failure will not be detected and that other systems might depend on the erroneous temperature sensor reading. For example, a patient heating or cooling system may fail to properly operate when relying on temperature measurement provided by a failed temperature sensor.
What is desired is a way to measure a patient""s core body temperature while minimizing patient discomfort and risk of injury. What is also desired is a way of assuring integrity of core body temperature measurements.
A Foley catheter having redundant temperature sensors includes a catheter body with a proximal end and a distal end, an inflatable balloon disposed near the distal end, an inflation lumen extending from the proximal end to the balloon for inflating and deflating the balloon, a drainage lumen extending from the proximal end to the distal end, at least one temperature sensor lumen extending from the proximal end to the distal end, and at least two temperature sensors, each having a wire and a sensor element, the sensor elements being disposed in the distal end of the catheter body and the wires extending through the catheter body drainage lumen.
The temperature sensors electronically couple with a control unit, which obtains a primary temperature reading from one of the temperature sensors and obtains a secondary temperature reading from the other temperature sensors. The control unit compares the primary and secondary temperature reading to determine a difference.
The control unit establishes a threshold. The threshold is the maximum acceptable difference between the primary and secondary temperature readings. This threshold, according to one aspect of the invention, is set manually by an operator. The control unit also includes an alarm so that when the difference between the primary and secondary temperature readings exceeds the threshold, the control unit activates the alarm.
The alarm is audible according to one aspect of the invention and is sounded on a speaker in communication with the control unit. According to another aspect of the invention, the alarm includes a video display and activation of the alarm provides a video signal to the video display. In yet another embodiment, the alarm simply shuts the control unit off.
A method of using a Foley catheter with redundant temperature sensors in accordance with the invention includes the steps of introducing a Foley catheter into the bladder of a patient and using the Foley catheter to drain urine from the bladder. The method also includes electronically coupling the temperature sensors to a control unit and activating the control unit to obtain the primary temperature reading and the secondary temperature reading from the redundant temperature sensors.
Obtaining two, or more, temperature readings facilitates redundancy. One aspect of the invention includes the step of comparing the primary temperature reading and the secondary temperature reading to determine whether both sensors are operational.
Another aspect of the invention includes three temperature sensors and an appropriate methodology for detecting sensor failure. Three sensors enables continued operation of the control unit to achieve meaningful temperature readings notwithstanding the failure of one of the temperature sensors. It can be appreciated that there are a variety of control and feedback methods that can accomplish continuous operation of the catheter, sensors and control unit during a failure of one of the sensors.
According to an aspect of the invention having two sensors, determining whether both sensors are operational is accomplished by comparing the primary temperature reading and the secondary temperature reading to determine a difference between the primary and secondary temperature readings. The control unit deactivates when the difference exceeds the threshold. Preferably, the sensors operate with an accuracy of +/xe2x88x920.1 degree Fahrenheit. Accordingly a temperature difference of a whole degree, for example, or more would typically indicate failure of one of the sensors.
According to an embodiment of the invention the controller establishes a temperature threshold within the range of 0.5-2 degrees Fahrenheit. More preferably, however, the temperature threshold is about 1 degree Fahrenheit so that the redundant sensors would operate safely in conjunction with a heat exchange catheter system for regulating patient body temperature.